NUTRITION LAB

The raw milk debate rages on

More and more consumers are forgoing standard milk in favor of "raw" milk, milk that's unpasteurized and unhomogenized, essentially straight from the udder of the cow.

Some seek out raw milk for its reportedly creamier, richer taste, but more choose it because they believe it's more healthful, a "living" food that can help fend off many illnesses, as varied as allergies and cancer. "Raw milk consumers are dedicated to building their immune systems," says Mark McAfee, founder of Organic Pastures, a raw dairy in Fresno.

The claims sound innocent enough, but the sale of raw milk is illegal in nearly two dozen states, and federal regulations prohibit producers in states where raw milk is legal, including California, from shipping it over state lines. The Food and Drug Administration cautions consumers against raw milk consumption and last year began cracking down on dairies, including McAfee's, for illegal distribution across state lines. (Organic Pastures pleaded guilty to the charge but continues to sell raw milk products -- legally -- throughout California.)

Claims about raw milk's health benefits are scientifically tenuous. Raw milk and pasteurized milk are equivalent in terms of protein, nutrient, fat and carbohydrate makeup, says Rusty Bishop, director of the Wisconsin Center for Dairy Research at the University of Wisconsin, Madison. After raw milk has been pasteurized, he says, "there's no difference in composition, other than that you've killed off a significant number of bacteria that were in the milk."

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Under the microscope

Bacteria, however, are at the crux of the controversy over raw milk.

Proponents argue that the milk naturally contains an array of beneficial bacteria and enzymes that give the immune system a workout and aid with digestion -- and that are destroyed by pasteurization. Meanwhile, dairy scientists such as Bishop argue that such beneficial bacteria (such as acidophilus and bifidobacterium) occur only in small amounts in raw milk, and that any enzymes the milk contains have no proven benefit for humans.

Federal officials maintain that pasteurization is crucial because the risk of contamination with harmful bacteria outweighs any potential benefits from beneficial, or probiotic, bacteria found in unprocessed milk.

Raw milk advocates point to a small, mostly European body of research to support their claims. A handful of studies have shown that children who grow up on farms appear to be less likely than other children to suffer from allergies such as hay fever and asthma. A separate body of research has begun to link that effect to unpasteurized milk -- though the evidence is preliminary, and somewhat mixed.

A study of about 100 children in Crete, published in the journal Clinical and Experimental Allergy in 2001, found a significantly reduced rate of allergies among urban (but not rural) children who drank unpasteurized milk. A study of more than 4,000 children in a rural county in England, published by the Journal of Allergy and Clinical Immunology in 2006, found that those children who drank unpasteurized milk were 40% less likely to have symptoms of eczema. A New Zealand study, published in the journal Allergy in 2002, found a similar effect on eczema.

But an analysis of data collected from more than 23,000 adult women in Iowa, published in the journal Cancer Causes and Control last October, revealed a slightly higher rate of asthma and eczema among those who said they had ever consumed unpasteurized milk, compared with those who hadn't.

Meanwhile, a far greater number of studies have linked raw milk and cheese to outbreaks of E. coli, salmonella, listeria and a bacterium called campylobacter. The pathogens aren't inherent to raw milk, but can get into the milk due to unsanitary conditions.

A report published by the Centers for Disease Control and Prevention in 2007 traced 45 outbreaks, causing more than a thousand illnesses and two deaths, to bacteria in unpasteurized milk or cheese between 1998 and 2005. "Raw milk could potentially have beneficial bacteria, but there's a higher likelihood that it has pathogenic organisms as well," says Lloyd Metzger, director of the Midwest Dairy Foods Research Center at South Dakota State University in Brookings and a spokesman for the Institute of Food Technologists, an association of food scientists.